Art of forming smooth surfaces on wood pulp



{No Model.)

G. 0. TOWLE. ART OF PORMING SMOOTH SURFACBS ON WOOD PULP. No. 424513.Patented Apr. 1, 1890.

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UNITED STATES PATENT OFFICE.

GEORGE C. TOlVLE, OF IIYDE PARK, MASSACHUSETTS.

ART OF FORMING SMOOTH SURFACES ON WOOD PULP.

SPECIFICATION forming part of Letters Patent No. &24,513, dated April 1,1890.

Application filed January 9, 1889. Serial No. 295.860. (No model.)

To all whom, 't may concrn:

Be it known that I, GEORGE O. TOWLE, of Hyde Park, in the county ofNorfolk and Commonwealth of M assachusetts, have inven ted certain newand useful Improvements in the Art of Forming Smooth Surfaces on lVoodPulp, of which the following is a specifieation.

IIeretofore it has been customary to fashion articles of wood pulp bymolding them or by sawing and cutting them into required shapes ,andfinishing the surfaces either by cutting or by sandpapering them, andsometimes by pressing them simply. It has been attempted to press suchsurfaces into figured shapes or letters; but such experiments, so far asI am aware, have been unsuccessful, because the letters or shapes werenot enduring, and especially would not continue through any process ofgilding or other liquid finishing. It is desirable to use wood pulp forthe construetion of calendar-stands or other articles for the desk, andfor plaques and other ornamental use, and to prepare the surfaces ofthese with a permanent smoothness of finish, and to make the surfaceswith raised or impressed letters and figures, bas-reliefs, and the like,and also to gild such surfaces,whether plain or ornamental, so as topreserve such surfaces when gilded or sized or painted.

In carrying out my improvements in the art or process of preparing,finishing, figuring, and ornamenting surfaces of wood pulp I take thearticle as prepared by cutting, sawing, or molding in the ordinary way,preferring for the surface which I am about to treat either a sawed orsandpapered surface to begin with, and first dip that surface in aliquid bath, which is by preference water moderately acidulated withnitric acid and used hot. Some other acids, as acetic acid, will producesimilar but not as good results, as will also some alkaline solutions,but with not so good results. The effect of this dipping of the surfacein a solution either acid or alkaline of the character herein describedis to raise or improve the slightly furred or napped character of thesurface. My next step is to dip this prepared surface in oil orotherwise cover it with a slight film of oil, using by preference eithermineral oil or linseed-oil. For plain or coarse work I mix paraffine orresin with the oil, this oiling of the surface servi ng to partiallyfill the pores and conbine with the next step in the process to cementthe nap and close the pores and form a base of resistance to any otherliquid finish that may be used, such as gilding or sizing or coloring.Third, I then press the surface so prepared by the other two steps inthe process with a heated die, This as to plain surfaees compresses thenap and the pores to asnooth or laid exterior, and by means of the heatand pressure sets or fiXes the oil and the fiber together, so as toinsure a permanent smoothness of surface; and for forming raised lettersor other ornamental figuring I use a die with such letters or figuringcut in its surface, using it under pressure in the same manner, but withthe effect to raise the letters or other ornamental figures or leavethem in relief on the pulpsurface by a process of partial compression ofthe surrounding surface and partial raising of the relief-surfaces, (theoperationbeing substantially the same when cameo-dies are used to formintaglo or indented letters or figures in the surface of the wood-pulparticle,) and the same method results not only in a smooth and permanentfinish of the plain surfaces in this casebut also in a complete andfixed relation of the raised or depressed figures. After the article hasbeen prepared and fixed by this method, the surface or surfaces soprepared may be further finished by sizing, gilding, or coloring withoutdetriment, without the disappearance of the figures or ornaments, andwith the appearance of a fine, smooth finished, gilded, or othersurface, all its lines of ornanent being preserved.

In the drawings aecompanying this specification, Figur-e l shows inperspective a molded or sawed block of wood pulp. Fig. 2 shows the samewith its upper surface a' dipped in the acidulated bath. Fig. 3 shows inperspective the same with the upper surface o? covered with a film ofoil. Fig. 4 shows in Vertical transverse section the same prepared blockin a press with a die ready to be inpressed upon the prepared surface.Fig. 5 shows in perspective the block after it has been pressed with theletters raised thereon, and Fig. 7 shows the same in Vertical trans-Verse section. Figs. 6 and 8 show in top plan IOO and in verticalsection, respectively, a plaque with a raised figure of a type-writer inthe middle pressed out of a sheet of pulp according to my method.

A is a block of Wood pulp. A' is the same after the dipping in acidsolution, with the furred surface a'. A is the same with the furredsurface coated with a film of oil at a A is the same-after pressu e withthe heated die, having the plain finished surface 60 and tleOraisedlettered su'rfaces also finished, as a B is the bottom, and B' B' arethe sides, of the table or platen holder for the block A which I use inmy press, and C is a die held 111 a plunger D and having the intagliofigure c cut in its operative side.

As the onstruction of press is immaterial to this invention, I do notshow its Construction further than the die and holder. I also use abloW-pipe E, arranged with the press so as to throw a fiame F upon thedie O to keep it suficiently heated.

X is a plaque with a finished upper sur face afi and a raised figuredsurface W, produced in the same method. a

In the course of my experiments in making this invention and ofpractically using the invention since, I have found that Watermoderately acidulated with nitric acid and used hot, as above described,gives the best results for the preliminary bath-that is to say, itloosens the surface fibers and, as it were, raises a fur or nap on thesurface and prepares the surface for the subscquent steps of theprocess; but I have found, also, that this bath may be used tepid oreven cold and produce similar results, but not so satisfactorly. I havealso tried as a preparatory bath water acidulated With sulphuricacidinstead of nitric acid, and it did not produce the required result. Ihave tried water acidulated with hydrochloric acid, and also a mixtureof water with a solution of potash, and also a mixture of water Withcommon soap, and also a mixture of water with a solution of ammonia, andin each of these cases I found that the same result was produced, butnot in so satisfactory a degree as with the use of nitric acid. Iconsider, therefore, a bath of water moderately acidulated With either hydrochloric acid or water rendered moderately alkaline by the use ofpotash, ammonia, or common soap an equivalent for the bath acidulatedwith nitric acid, hereinbefore referred to; but I do not consider a bathacidulated With sulphuric acid as an equivalent.

I claim as new and of my invention- The art or process of fixing apermanent, plain, or embossed smooth surface on articles of Wood pulp,consisting in treating the surface of the plain stock first with a bathof Water acidulated with nitric acid or its described equivalent, thenwith a film of oil, and then subjecting it to pressure with a heateddie, essentially as set forth.

GEORGE C. TOWLE. witnesses:

HERBERT MANSFIELD, GEORGE V. WHITE.

